Sapphire Radeon HD 6950 & 6970 review - Intro, cont'd
Author: Luka Rakamaric
Date: 04 Mar 2011

The biggest change is the architecture. From the 2900XT, AMD has been using the Very Long Instruction Word 5 architecture. Now it goes away, unlike the 6800 series, which still kept it. The new architecture is VLIW 4, so you get a 4 stage pipeline, but more of them. We have said many times before, in games you couldn’t utilize all of the shaders. AMD said their average utilization was 3.4. With the general purpose GPU usage, they had to react. The step down to a 4 level parallelism is a logical choice. They removed the last, so called t-unit. It was tasked with performing transcendental operations. To compensate, the first three now work together when you get a transcendental operation. In the worst case, you can do only on transcendental and one INT/FP operation, as opposed to the one transcendental and four INT/FP operations in the Cypress (5800 series) architecture. However, the t-unit is the largest. This enabled ATI to stick more SPUs in the chip, with a 20% increase from 20 to 24. Each SP is slightly bigger to compensate for the additional t-unit functionality, but in return you get much better FP64 operations, which is great for compute purposes.

The 6970 measures 10.5 inches long, which is identical to the 5870, as well as the new 6950. The cooler on both new cards is the same, and the only visible difference is the power connector configuration. The 6950 uses 2x 6 pin, and the 6970 with its 250W thermal envelope must use one 6 pin and one 8 pin. The 6950 has slightly less processors at 1408, as well as a same percentage of missing TMUs, at 88. However, the memory configuration as well as ROPs stayed the same. That is the only major difference, aside from chip clocks. The 6970 has a 10% edge here.

Test system

- Intel Core i7-920
- Gigabyte GA-X58A-UD9
- PC Power & Cooling Turbo Cool 1KW-SR
- OCZ Reaper 1600 MHz, 7-7-721 3x2 GB
- Western Digital Raptor X 150 GB
- HP LP3065 screen

We decided to do benchmarks the two most common resolutions we will see on today’s screens, 1920x1080 and 1680x1050, plus the 2560x1600 to see how well the cards do in the 30’’ screen territory. While the first two are not that far apart, they are what most people use today.

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